1. Field of the Invention
The present invention relates to a muffler, and more particularly to a muffler used in a reciprocating compressor.
2. Description of the Conventional Art
Generally, mufflers applied to compressors are classified into a suction muffler connected to a fluid suction section of a compressor and a discharge muffler connected to a fluid discharge section of a compressor.
Such suction and discharge mufflers serve to attenuate a pulsation phenomenon periodically generated during repeated fluid suction and discharge operations of a compressor, to which those mufflers are applied, thereby allowing the compressor to smoothly suck and discharge fluid. These mufflers also serve to shield impact noise generated in opening and closing operations of a valve and noise resulting from flowing of fluid so that those noise cannot be externally transmitted from the compressor, thereby achieving a silent operation of the compressor.
FIG. 1 is a sectional view illustrating an example of a hermetic reciprocating compressor respectively provided with conventional mufflers at suction and discharge sections thereof.
As shown in FIG. 1, the reciprocating compressor includes a casing 1 filled with a desired amount of oil, an electric motor mechanism installed in a lower portion of the casing 1 in the interior of the casing 1 and adapted to generate a drive force in response to electric power externally applied thereto, and a compression mechanism installed at an upper portion of the casing 1 in the interior of the casing 1 and adapted to receive the drive force from the electric motor mechanism so as to conduct gas sucking and compressing operations.
The compression mechanism includes a frame 2 fixedly mounted to the casing 1 in the interior of the casing 1, a cylinder 3 fixedly mounted to a portion of the frame 2, and a drive shaft 5 extending vertically through a central portion of the frame 2 while being fitted in a rotor 4B included in the electric motor mechanism so that it is coupled to the rotor 4B. The drive shaft 5 is provided at an upper end thereof with an eccentric portion. The compression mechanism also includes a connecting rod 6 coupled to the eccentric portion of the drive shaft 5 and adapted to convert a rotating movement into a reciprocating movement, a piston 7 connected to the connecting rod 6 and slidably received in the cylinder 3 in such a fashion that it reciprocates in the cylinder 3, a valve assembly 8 coupled to the cylinder 3 and adapted to control suction and discharge of refrigerant gas, and a head cover 9 coupled to the valve assembly 8 and defined with a desired discharge space. The compression mechanism further includes a suction muffler 10 coupled to a portion of the head cover in such a fashion that it communicates with a suction inlet of the valve assembly 8, and a discharge muffler DM mounted to the cylinder 3 in such a fashion that it communicates with a discharge outlet of the valve assembly 8.
In association with respective orientations of the above-mentioned elements, the upward direction corresponds to the direction toward the upper portion of the plane in FIG. 1.
As shown in FIG. 2, the muffler 10 is provided with a muffler inlet 11 directly communicated with a refrigerant line SP extending through the casing 1 or arranged in the interior of the casing 1.
The muffler inlet 11 communicates with a first reservoir S1 defined, in the form of an expansion chamber, in a central portion of the muffler 10.
The first reservoir S1 communicates with a second reservoir S2 defined, in the form of an expansion chamber, beneath the first reservoir S1 via a first conduit having a small cross-sectional area. A third reservoir S3 is defined, in the form of an expansion chamber, above the first reservoir S1. The third reservoir S3 serves as the Helmholtz reservoir.
The second reservoir S2 communicates with a muffler outlet 12 communicating with the valve assembly 8 via a second conduit 16 extending vertically into the second reservoir S2 through the third reservoir S3.
A resonant aperture 17 is formed at an upper portion of the second conduit 16 arranged in the third reservoir S3 so that it constitutes the Helmholtz Resonator, together with the third reservoir S3.
In FIGS. 1 and 2, the reference numeral or character 4A denotes a stator, 18 an oil discharge port, C a support spring, and O an oil feeder. In addition, the reference numerals 13 and 14 denote partition walls, respectively.
Now, an operation of the hermetic reciprocating compressor provided with the above mentioned conventional mufflers will be described.
When the rotor 4A is rotated by a mutual electromagnetic force generated between the stator 4A and the rotor 4B in response to electric power applied to the electric motor mechanism, the drive shaft 5 rotates along with the rotor 4B. The rotation of the drive shaft 5 is converted into straight reciprocating movements by the connecting rod 6 coupled to the eccentric portion of the drive shaft 5. The reciprocating movements is transmitted to the piston 7 which, in turn, reciprocates in the interior of the cylinder 3 to compress refrigerant gas and to discharge the compressed refrigerant gas. Pressure pulsation and noise, which may be generated during the above-mentioned operations of the piston 7, flow in a direction opposite to the flowing direction of the refrigerant gas so that they are attenuated by the muffler 10.
The procedure for attenuating the pressure pulsation and flowing noise by the conventional mufflers will now be described.
During a stroke of the piston 7 from an upper dead point to a lower dead point, refrigerant gas filled in the second reservoir S2 is forced to be sucked into the interior of the cylinder 3, that is, a compression chamber, via the second conduit 16 and muffler outlet 12 while opening a suction valve of the valve assembly 8. Simultaneously, new refrigerant gas is introduced into the second reservoir S2 via the muffler inlet 11, first reservoir S1 and first conduit 15. On the other hand, during a stroke of the piston 7 from the lower dead point to the upper dead point, the suction valve of the valve assembly 8 is closed. In this state, a discharge valve of the valve assembly 8 is simultaneously opened. Therefore, compressed refrigerant gas is discharged into a discharge space DS defined in the head cover 9.
In the procedure in which the suction and discharge of refrigerant gas are repeated, a repetitive pressure pulsation occurs continuously in the muffler 10 and head cover 9. Such pressure pulsation is propagated to each flow path defined in the muffler 10. As this pressure pulsation passes the second conduit 16, second reservoir S2, first conduit 15, and first reservoir S1, they are gradually attenuated, and finally dissipated. Therefore, there is little pressure pulsation at the muffler inlet 11. Accordingly, the refrigerant gas can be smoothly introduced.
Meanwhile, noise generated during the suction of refrigerant gas is converted into heat energy in accordance with a diffusion and dissipation thereof occurring when it passes through the conduits 15 and 16, and reservoirs S1, S2 and S3, so that it is attenuated. In particular, noise of a specific frequency is attenuated by the helmholtz Resonator composed of the resonant aperture 17 of the second conduit 16 and the third reservoir S3.
In the above mentioned noise attenuation method, in which attenuation of noise is achieved using a simple resonation effect and the Helmholtz Resonator, however, it is necessary to use an excessively large volume for each reservoir. Therefore, there is a problem in that the whole muffler volume is undesirably increased.
Furthermore, the procedure of converting pulsation energy of noise into heat energy in accordance with a diffusion and dissipation causes an increase in muffler temperature resulting in an increase in the specific volume of refrigerant gas. Therefore, there is a problem in that the efficiency of the compressor is degraded.
The periodic pressure pulsation of the compression also causes a periodic pulsation of the internal muffler pressure resulting in a momentary counter pressure gradient serving to generate a reverse flow of refrigerant gas. Therefore, the introduction amount of refrigerant gas is reduced, thereby causing degradation in the efficiency of the compressor.
Therefore, an object of the invention is to provide a muffler capable of having a reduced volume while providing an improved muffling effect, and reducing a generation of heat energy.
Another object of the invention is to provide a muffler capable of avoiding the generation of a reverse flow of refrigerant gas resulting in a reduced introduction amount of refrigerant gas, thereby preventing a degradation in the efficiency of a compressor to which the muffler is applied.
In accordance with the present invention, these objects are accomplished by providing a muffler comprising: a muffler inlet arranged in the muffler body, the muffler inlet communicating a refrigerant line extending into the interior of the casing; a first reservoir defined, in the form of an expansion chamber, in the muffler body above the muffler inlet; a second reservoir defined, in the form of an expansion chamber, in the muffler body beneath the first reservoir; a first conduit having a reduced cross-sectional area, the first conduit serving to connect the first and second reservoirs to each other; a second conduit having a reduced cross-sectional area, the second conduit serving to communicate the second reservoir with a muffler outlet provided at the muffler body; a third reservoir defined, in the form of an expansion chamber, defined in the muffler body around the second conduit above the second reservoir, the third reservoir serving as the Helmholtz reservoir; and an interference member fixedly mounted in at least one of the first and second conduits.